You said you can give me an idea? My troubles make me go use your
help. I get WA, but all my test runnings for this program were
successfull. This is the source:

// solution for superlong sums. version 3.0
#include <stdio.h>
typedef unsigned long T;
int main()
{
  T amo, nin=0, i, j=0;
  unsigned int las=0, a, b;
  unsigned char fpr; // output in first time

  fpr = 2;
  las = 0;

  scanf("%d", &amo);

  for (i=1; i<=amo; i++)
  {

  scanf("%d", &a);
  scanf("%d", &b);

  if (a+b < 9)
   {
      if ((fpr == 0) || (las != 0))
    {
    printf("%d", las);
    fpr = 0;
    }; // if not in first time or las<>0
      for (j=1; j<=nin; j++) printf("9");

      if (nin>0) fpr = 0;

      nin = 0;
      las = a+b;
   }; // if a+b<9

  if (a+b == 9)
   {

   nin++;

   }; // if a+b == 9

  if (a+b > 9)
   {

   printf("%d", las+1);
   fpr = 0;// !!!!!!

   for (j=1; j<=nin; j++) printf("0");
   nin = 0;
   las = a + b - 10;

   }; // if a+b > 9
  };

if ((fpr == 0) || (las != 0))  printf("%d", las);

for (j=1; j<=nin; j++) printf("9");


return 0;
} // main